568 THE INTESTINAL CANAL, BY E. KLEIN AND E. VERSON. 



Whilst the Peyer's patches constantly occupy the border of 

 the intestine opposite the attachment of the mesentery, isolated 

 or solitary follicles are distributed irregularly over its whole 

 surface. These, like the Peyer's patches, are much more closely 

 arranged in the lowest parts of the ileum. The number of 

 Peyer's patches in the small intestine varies considerably. 

 Authors calculate twenty to be about the average, though no 

 definite limits can be given on either side. Where they are 

 very numerous, they extend into the upper parts of the tube. 

 Middeldorpf observed them even in the lower curvature of the 

 duodenum. 



GLANDS. The secreting glands of the small intestine are 

 constructed upon two different types, the acinous and the tubu- 

 lar, and are named after their discoverers, the former Brunner's 

 glands, the latter, the Lieberkuhnian follicles. 



Brunner's glands agree exactly in their structure with that 

 of other acinous glands of mucous membranes, and in man 

 form groups of from five to ten acini, which open into a single 

 excretory duct that traverses the mucous membrane, and opens 

 on the surface. The diameter of the acini amounts to about 

 0*07 to 0'14 of a millimeter, and they consist of a structureless 

 vesicle, the interior of which is lined with somewhat flattened 

 cylindrical cells. The excretory duct is lined by similar epi- 

 thelium. 



The glands of Brunner lie imbedded in the submucous con- 

 nective tissue, and form small masses, which may however 

 attain sufficient size to cause the whole tunica nervea to dis- 

 appear; and are bounded on the one side by the muscular 

 tunic, and on the other by the muscularis mucosse. The latter, 

 however, forms no absolute limit, some of the acini being occa- 

 sionally found projecting through it against the mucous layer, 

 whilst, on the other hand, a few slender fasciculi of the muscle 

 cells also accompany the connective tissue between the glandu- 

 lar vesicles, and then divide. 



The greater portion of the glands of Brunner are found in 

 the vicinity of the pylorus. In man, however, a few groups 

 of these glands are distributed lower down the canal, whilst in 

 other animals the whole series of glands form a single coherent 



